1. Field of the Invention
The present invention relates to a communication system which is capable of interruption talk during data transmission, and, more particularly, to a radio communication system which is capable of interruption talk during data transmission, by polling between a fixed central station and a plurality of mobile terminal units.
2. Description of the Prior Art
A conventional radio communication system of this kind comprises a central station and a plurality of terminal units, such as mobile units. The central station sends digital polling signals to the terminal units and receives response data signals from the terminal units, respectively.
During the time when data transmission is performed by a polling operation, etc, it has been inhibited to make a free talk from terminal units in order to avoid any data destruction by collision. This has caused inconveniences, such as an impossibility of talk even in an emergency, or the like.